一、文件操作

二、网络请求

1. Http
2. HTTPClient
3. 第三方请求dio
   dio（English | 中文简体）是Flutter中文网开源的一个强大的Dart Http请求库，支持Restful API、FormData、拦截器、请求取消、Cookie管理、文件上传/下载、超时等...

• ①添加依赖dio: ^3.0.3
• ②接口类

class Apis {
  static const String BASE_HOST = "https://www.wanandroid.com";
  /// 首页轮播
  static const String HOME_BANNER = BASE_HOST + "/banner/json";
  /// 首页列表
  static const String HOME_ARTICLE_LIST = BASE_HOST + "/article/list";
}

• ③dio方法封装

///dio 方法封装
class ApiService {
  Dio dio = Dio();

  ///  获取首页轮播数据
 getBannerList() async {
    try {
      Response response = await dio.get(Apis.HOME_BANNER);
      if (response.statusCode == 200) {
        return response;
      } else {
        throw Exception('网络异常！');
      }
    } catch (e) {
      return print(e);
    }
  }

实现异步有两种方式，Future和async、await，Future实现异步使用的API稍微复杂点，在Dart1.9中加入了async和await关键字，简化了异步写法
async：申明该方法为异步方法
await：阻塞式访问

• ④获取数据模型：json转换为数据模型

class BannerModel {
  List<BannerBean> data;
  int errorCode;
  String errorMsg;

  BannerModel({this.data, this.errorCode, this.errorMsg});

  BannerModel.fromJson(Map<String, dynamic> json) {
    if (json['data'] != null) {
      data = new List<BannerBean>();
      json['data'].forEach((v) {
        data.add(new BannerBean.fromJson(v));
      });
    }
    errorCode = json['errorCode'];
    errorMsg = json['errorMsg'];
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    if (this.data != null) {
      data['data'] = this.data.map((v) => v.toJson()).toList();
    }
    data['errorCode'] = this.errorCode;
    data['errorMsg'] = this.errorMsg;
    return data;
  }
}

class BannerBean {
  String desc;
  int id;
  String imagePath;
  int isVisible;
  int order;
  String title;
  int type;
  String url;

  BannerBean(
      {this.desc,
      this.id,
      this.imagePath,
      this.isVisible,
      this.order,
      this.title,
      this.type,
      this.url});

  BannerBean.fromJson(Map<String, dynamic> json) {
    desc = json['desc'];
    id = json['id'];
    imagePath = json['imagePath'];
    isVisible = json['isVisible'];
    order = json['order'];
    title = json['title'];
    type = json['type'];
    url = json['url'];
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['desc'] = this.desc;
    data['id'] = this.id;
    data['imagePath'] = this.imagePath;
    data['isVisible'] = this.isVisible;
    data['order'] = this.order;
    data['title'] = this.title;
    data['type'] = this.type;
    data['url'] = this.url;
    return data;
  }
}

• ⑤使用获取的网络数据

class HomePage extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    // TODO: implement createState
    return _HomeScreen();
  }
}

class _HomeScreen extends State<HomePage> {
  int _page = 0;
  BannerModel banners = BannerModel();
  ArticleModel _articleModel = ArticleModel();
  var scrollController = ScrollController();

  @override
  void initState() {
    super.initState();
    getBanners();
    getArticleList();
  }

  void getBanners() async {
    await ApiService().getBannerList().then((value) {
      //解码返回数据
      var data = json.decode(value.toString());
      //设置新数据，刷新状态
      setState(() {
        banners = BannerModel.fromJson(data);
      });
    });
  }

  void getArticleList() async {
    await ApiService().getArticleList(_page).then((value) {
      //解码返回数据
      var data = json.decode(value.toString());
      //设置新数据，刷新状态
      setState(() {
        _articleModel = ArticleModel.fromJson(data);
      });
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: ListView.builder(
        itemBuilder: itemView,
        controller: scrollController,
        itemCount: _articleModel.data.datas.length + 1,
      ),
    );
  }

  Widget itemView(BuildContext context, int index) {
    if (index == 0) {
      return Container(
          width: double.infinity,
          child: AspectRatio(
            aspectRatio: 16 / 9,
            child: Swiper(
              itemBuilder: (BuildContext contxt, int index) {
                return Image.network(banners.data[index].imagePath,
                    fit: BoxFit.cover);
              },
              itemCount: banners.data.length,
              pagination: SwiperPagination(),
              //显示indicator
//                control: SwiperControl(), //显示箭头
              loop: true,
              autoplay: true,
            ),
          ));
    }
    ArticleBean item = _articleModel.data.datas[index - 1];
    return ItemArticleList(item: item);
  }
}